Correct option is A
Statement Analysis:
All poets are writers: The 'Poet' circle is entirely inside the 'Writer' circle.
Some writers are thinkers: An intersection exists between 'Writer' and 'Thinker'.
All thinkers are critics: The 'Thinker' circle is entirely inside the 'Critic' circle.

Conclusion Analysis:
Conclusion I (Some poets are critics): False. In the basic diagram, 'Poet' and 'Critic' do not touch. While it's a possibility, it is not a definite conclusion.
Conclusion II (Some writers are critics): True. Since some 'Writers' are 'Thinkers' and all 'Thinkers' are 'Critics', that overlapping portion of 'Writers' is definitely 'Critics'.
Final Answer: Only Conclusion II follows.